For the few who haven’t heard of this great book: Spillover by David Quammen was written in 2014 and it was re-discovered during the COVID-19 pandemic because almost prophetic in its descriptions and predictions.
Of course, I had to give it a good read; Here are 10 things I learned from reading Spillover in pandemic times.
If you are tired and you want the summary, you’ll find it here –>
1. Everything comes from somewhere
Everything comes from somewhere: Earth’s energy from the Sun, microchips from metal reservoirs somewhere underground, and germs from an ancestral germ in some other species.
The malaria parasite lives in mosquito, the avian influenza in birds, and the SARS-COVID in bats. That’s their respective usual place, they didn’t come from nowhere, they came from somewhere. This is the clever idea at the base of a pandemic: viruses and bacteria that can cause severe infectious diseases, normally live “peacefully” in some other species or places before some evolutionary pressure or simply random chance lead to the evolution of a particular trait that can generate an “improved” version of the germ.
These evolved germs can now infect, spread and/or replicate better, faster or simply more efficiently. This leads to a larger population which increases the chance of a spillover: an infection cross-species. That’s why a zoonotic disease is harder to eradicate: because it hides in other species; the so-called reservoir species.
2. Viruses are most problematic
Viruses are the most problematic. They evolve quickly, they are unaffected by antibiotics, they can be elusive, they can be versatile, they can inflict extremely high rates of fatality, and they are fiendishly simple, at least relative to other living or quasi-living creatures. Ebola, West Nile, Marburg, the SARS bug, monkeypox, rabies, Machupo, dengue, the yellow fever agent, Nipah, Hendra, Hantaan (the namesake of the hantaviruses, first identified in Korea), chikungunya, Junin, Borna, the influenzas, and the HIVs (HIV-1, which mainly accounts for the AIDS pandemic, and HIV-2, which is less widespread) are all viruses. The full list is much longer.
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“Viruses have no locomotion,” according to the eminent virologist Stephen S. Morse, “yet many of them have traveled around the world.” They can’t run, they can’t walk, they can’t swim, they can’t crawl. They ride.
If you were wondering why viruses cause so many problems, now you have an answer. They’re fast, small, and we are never well-equipped to deal with them. With so many types and numbers of viruses, with so diversified niches and mechanisms, it’s just matter of chance before a virus can spillover and hit another unknowing species…
3. Researchers are the heroes of infectious diseases
Most of the stories and adventures described in the book talk not about the science or the victims, but about the protagonists: the scientists and researchers.
Those who spend their times, efforts and sometimes own health for the humans’ sake to better understand, treat or eradicate the many diseases emerging all over the world. Over the years, and especially during the COVID-19 pandemic, more and more attention was placed on doctors and physicians as “heroes” who bravely attend our sick family and friends. But we do have to remember: doctors without medicines are like cars without fuel.
It is thanks to those experiments that we know which drugs can work, it is thanks to those studies that we know how the drug works and it is thanks to those clinical trials that we know how well the drug works. It is the basic research and science behind every treatment and patient that empower the physicians to do their job.
4. Germs and hosts constitute an ecological equilibrium
If germs constantly infect their reservoir species, how come is this species fine? How come doesn’t it go towards extinction like humans could do without their modern and sophisticated medical technology?
Germs and their hosts have evolved together in an arm-race, often for many eons, in which both tried to win over the other. Often when we see such interactions, the two players have already reached a sort of ecological equilibrium, in which, for example, the virus doesn’t cause too many problems and can replicate mildly. It’s important to remember that:
not every virus is “a piece of bad news wrapped up in a protein”
and that:
A virus doesn’t necessarily achieve anything by making its host sick. Its self-interest requires just replication and transmission.
Indeed, viruses don’t have any “bad intentions” to hurt us, and most of the time, killing us rapidly would simply cut their chances to replicate and thus spread more.
What breaks this equilibrium? A good example is a spillover! When the virus exits its usual host and reaches another organism, then the equilibrium is broken, and everything is valid. All the established mechanisms come loose and war enrages. If the virus replicates extremely efficiently is because it didn’t yet adapt well to the new host, and it’s simply carrying what “it had learned before” to the new situation.
5. Bats harvest many diseases
Bats are extremely common: they represent 25% of all mammal species and they are extremely diverse and abundant!
On one hand bats are so common that even if they carry a “typical” amount of infectious diseases in their populations, it is perceived as a huge slice compared all other mammals.
On the other hand, however, bats seem to harvest more diseases than “normal”! They are extremely numerous and social. They are very long-lived and can fly. Not only that, but they live in very crowded environments and create complex networks that can replenish populations even after immunization has occurred.
In summary, there’s a lot about bats that makes them special, but there’s not much to be surprised of when we see new infectious diseases coming from them.
6. There are more viruses out there we cannot detect
Considering how many (in quantity and diversity) viruses exist out there, and how many host species they could “live in”, it’s very likely that many new viruses are waiting to be discovered, hidden from everyone, until they spillover and make themselves noticed.
How many such bugs may be working their way through large-scale livestock operations around the globe? How many RNA viruses may be achieving high rates of evolution (because they replicate quickly, they often mutate, their populations are big, and the herds are big too) in our factory farms? What are the odds, given such numbers, of a mutation that facilitates spillover?
We physically cannot monitor all biological processes occurring in nature, and after all, not even in our livestock. If you think about it, if we haven’t yet met a virus we cannot even check for its presence, because deep down, we need to have some information about it to develop a diagnostic test.
7. An infected population reaches immunity
It is more or less intuitive, and very well predicted by SIR-like models that the spread of a virus depends on the balance between Susceptible, Infectious, or Recovered individuals. A certain fraction of the population becomes no longer susceptible after it has died or has turned immune.
As a consequence only alive individuals that has still not been exposed to the virus, can continue the spread of the disease. In practice, you need a minimum number of susceptible people to keep a non-zoonotic infection alive, otherwise it would go extinct. As we mentioned, since zoonotic diseases can “always” fall back on their reservoir species, it is hard to eradicate it completely, but reducing the number of susceptible individuals is the best strategy we can take to at least “send” new threats back to those reservoirs. This is a good moment to point out that vaccination is the most effective way we have to reduce that number of susceptible people in the population.
8. It’s all about opportunity
They don’t come after us. In one way or another, we go to them.
Since germs are always somewhere, waiting to be discovered, the fact that we are exposed to new infectious diseases, mostly depends on us! Humans are taking over the world, expanding and exploring every last hidden corner left on Earth.
By laws of numbers, sooner or later, we are bound to encounter a new threat that could lead to a new spillover. Remember, germs don’t have interest in hurting us, just to replicate; so if we do have our interests in surviving, the best thing we can do is to give germs less opportunity by respecting their space and interfere less with their ecological environments.
9. We should expect more pandemic in the future
As huge perturbations of nature’s equilibrium come to pass on Earth, we should expect humans to have more interactions with “previously hidden” germs.
The climate crisis, loss of biodiversity and increase of extreme weather events, are only a few examples suggesting that sooner or later humans and a new germs will be pushed together. Higher chances of global pandemics, were not only to be expected, but they were somewhat predicted.
A talking about predictions, we didn’t stay still; you can now check for yourself Spillover a new online tool for the Ranking the risk of animal-to-human spillover for newly discovered viruses.
10. The real pandemic is Homo sapiens
An entomologist named Alan A. Berryman addressed it some years ago in a paper titled “The Theory and Classification of Outbreaks.” He began with basics: “From the ecological point of view an outbreak can be defined as an explosive increase in the abundance of a particular species that occurs over a relatively short period of time.” Then, in the same bland tone, he noted: “From this perspective, the most serious outbreak on the planet earth is that of the species Homo sapiens.”
No matter how we put it, Homo sapiens has been and is the most influential species on Earth. It has brought immense visible changes to virtually all spheres of importance on the planet and to some extent even the universe. Being a successful species on Earth is not something we should victimize ourselves for; but we should definitely keep in mind our space, our role and its relationship to the place we evolved from.
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